How Long Does Insulin Last?

A woman goes to the doctor and has an HbA1c of 7.6. The doctor analyzes the last two months and discovers that her blood sugars were 40 mg/dL higher the second month (that’s 2.2 mmol). After talking with the patient, the doctor discovered that the patient had been using Lantus for 40 days, 25% over the recommended length. Clearly, insulin potency matters.

Photo Credit: Jeff Mather

So today let’s talk about how long it lasts and what can cause it to go bad.

The general rule is that:

Insulin is good until the expiration date on the bottle.

Opened vials do not need to be refrigerated & last 30 days.

Some older insulins like Novolin last 7 days after opening.

Insulin can last for less time in some cases. For example, freezing it will damage the potency. There are other, harder to track factors can have an impact like exposure to sunlight, agitation of the liquid, and the frequency of drawing insulin from the vial.

The major thing that affects insulin is heat. Most insulinmanufacturers recommend that you keep insulin below 86 F / 30 C. Eli Lilly notes that their insulin loses about 1% of potency per month at room temperature. Refrigerated, however, it only loses .1% per month. Above 86 F / 30 C, that degradation accelerates quickly.

Heat is especially a concern if you get your insulin from a mail order source. In the summer, be on the lookout for insulin that may have been left in the sun either during transit or at your home.

You can get a lot more details in this Diabetes Care journal article, including guidance from sanofi-aventis, Eli Lilly, Novo Nordisk, and the ADA.